I had it from the library in the 90s and I remember reading it multiple times, but can't remember the title (or the important geography!).
It is about a girl during wartime. I can't remember if she's Japanese or Korean, because I think I was too little to understand when I read it. She has an older sister called Ko, who has to dress like a boy to avoid rape from enemy troops. She and her sister and their mother are trying to get to safety. At one point the older sister gets a job in a sewing shop, but she's looked down on by all the other workers. Then, she demonstrates she can sew two pieces of white fabric together using red thread, and it doesn't show, and they are impressed by her skill and accept her. The mother dies at the end.
I really wish I remembered more - I can see some of the illustrations in my mind's eye! Help me out?